To maximize the transmission capacity of an optical communication system, a single optical fiber may be used to carry multiple optical signals in what is called a wavelength division multiplexed system (hereinafter a WDM system). The multiple optical signals may be multiplexed to form an aggregate multiplexed signal or WDM signal with each of the multiple signals being modulated on separate wavelengths referred to as channels. Modern WDM systems have a high traffic capacity, for example, a capacity to carry 100 or more channels at 100 gigabits per second (hereinafter Gb/s) per channel, or more.
The optical transmission system may include a relatively long trunk path (e.g., optical fiber) that may be terminated at a transmitting and/or receiving trunk terminal. The optical transmission system may further include one or more branching units situated along its trunk path. Each branching unit (BU) may be connected to a branch path (e.g., optical fiber) that terminates in a transmitting and/or receiving branch terminal. Each BU may include one or more integral optical add/drop multiplexers (OADM). Channels or wavelengths may be added to and/or dropped from the trunk path of the optical transmission system via the OADMs to direct optical signals on selected channels from and to the branch terminals.
Off-shore branch stations, such as oil and gas platforms, house branch terminal equipment to communicatively couple optical fibers to the trunk path. The branch terminal equipment may terminate branch optical fibers that couple the same to the trunk path, e.g., by way of a branching unit (BU) that includes an OADM arrangement for add/drop functionality. In any event, the optical fiber and associated components (e.g., repeaters, amplifiers, connectors, and so on) may collectively be referred to as a branch path. Subsea umbilical assemblies that include optical fiber, and in some cases power conductors and other elements, may form at least a portion of the branch path. Risers and other such vertical conduit devices may extend from the sea floor and allow the subsea umbilical assembly to couple to topside branch terminal equipment.
Unfortunately, the failure of a subsea umbilical assembly, such as an optical fiber failure due to a cable cut or other mechanical damage, connector path failure, or other interruption, may result in loss of communication between the branch terminal and the trunk path. Operations to repair such a subsea fault often require specialized equipment, e.g., remote operated vehicles (ROVs), and extended periods of time to complete. Downtime during repair of the riser may impact other critical functions of the riser such as delivery of electrical power, fluid and hydrocarbon transfer, and communications between the platform and other elements of the subsea infrastructure. Redundancy of optical fibers within the subsea umbilical assembly may allow for reallocation to “spare” optical fiber pairs. However, such spare optical fiber may not be available in already deployed systems, and riser constraints may significantly complicate bringing spare optical fibers topside.